1. Field of the Invention
The invention relates to the field of semiconductor processing and in particular to activation of ion implanted dopants.
2. Description of the Prior Art
Ion implantation is widely use to dope silicon for making shallow junction devices. The host lattice damage caused by ion implantation must be repaired by annealing in order to activate the dopant and to recover carrier mobility. Post implantation annealing, which is typically undertaken at 800.degree.-1000.degree. C. for 30 minutes, or rapid thermal annealing, at 1100.degree. C. for one second, is typically performed for lattice damage repair subsequent to dopant ion implantation. However, in heavily-doped silicon, such as silicon having 10.sup.20 ions per cm.sup.3 or more, these annealing procedures are incapable of achieving complete activation of the dopants. This failure of complete activation has been an unsolvable and perplexing problem for researchers in this field beginning from the 1960s to continuing to the present. While raising the temperature to provide higher temperature annealing is capable of also realizing better activation of dopants, annealing at these higher temperatures increases the thermal budget and broadens the junctions which are formed, which in the case of small devices results in an unacceptable broadening.
Moreover, as device processing rules decrease below the length of a wavelength used in the photolithographic patterning, it becomes necessary to maintain the shallow junction depths in proportion to the reduction in the lateral dimensions in order to maintain operability of the device. Moreover, as the device junctions and channels become smaller, signal strength decreases with decreasing current densities so that if an attempt is made to keep signal strengths at levels normally required within integrated circuits, current densities within the doped channels dramatically increase requiring increased conductivities to avoid overheating and to meet the performance requirements.
Therefore, what is needed is some means whereby conductivity of semiconductor material may be substantially increased without the use of high temperature annealing or other processes which would tend to broaden junctions or be subject to other defects of the prior art.